From Electron Cloud
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==Find range of true values in a std::vector<bool>== | ==Find range of true values in a std::vector<bool>== | ||
+ | <pre> | ||
std::vector<bool> m_vec; | std::vector<bool> m_vec; | ||
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return m_vec.rend() - found; | return m_vec.rend() - found; | ||
} | } | ||
+ | </pre> |
Revision as of 05:31, 15 June 2015
Stringify a define
If you would like to pass a string into a define via the compiler -D directive, but need to use it as if it was a quoted #define, it takes a pair of macros (verified to work on g++ and also Visual Studio):
#define STRINGIFY_IMPL(S) #S #define STRINGIFY(s) STRINGIFY_IMPL(s)
then it can be used like this:
QFile uiFile(":" STRINGIFY(UI_FILE));
and in the .pro file if using Qt:
DEFINES += UI_FILE="some.ui"
so when it's compiled:
g++ foo.cpp -DUI_FILE=some.ui ...
(oh noes, it's DUI!)
Find range of true values in a std::vector<bool>
std::vector<bool> m_vec; void update(int index, bool value) { if (index < 0) return; if (uint(index) >= m_vec.size()) m_vec.resize(index * 2 + 1); m_vec[index] = visible; } int firstTrueIndex() const { auto found = std::find(m_vec.begin(), m_vec.end(), true); if (found == std::end(m_vec)) return -1; return found - m_vec.begin(); } int lastTrueIndex() const { auto found = std::find(m_vec.rbegin(), m_vec.rend(), true); if (found == m_vec.rend()) return -1; return m_vec.rend() - found; }